1. Field of the Invention
The present invention relates to a gas barrier sheet improved in gas barrier properties and a manufacturing method thereof.
2. Description of the Related Art
Gas barrier sheets have barrier properties to oxygen or water vapor and such gas barrier sheets have been proposed which includes inorganic oxide films comprising silicon oxide or aluminum oxide formed on a base material as a gas barrier film. Such gas barrier sheets are excellent in transparency and thereby the demand for gas barrier sheets has greatly been expected as packaging materials for foods and medicines, as well as protective materials for electronic parts and display devices, and back cover sheet materials for solar cells.
For a film deposition method of a gas barrier film comprising inorganic oxides, ion plating has been adopted in addition to vacuum deposition or sputtering. A gas barrier film deposited by the ion plating is advantageous over a gas barrier film deposited by vacuum deposition in view of adhesion to a base material and denseness and is comparable to the gas barrier film deposited by sputtering. On the other hand, deposition of the gas barrier film by ion plating has a feature that a deposition speed is higher than that of sputtering and is as high as that of vacuum deposition.
In the deposition method of the gas barrier film, a base material is subjected to a pre-treatment just before the deposition of the gas barrier film (refer to Japanese Patent Laid-Open Nos. 7-80984 (paragraph 0016), 2000-15737 (paragraph 0022), 2004-160836 (paragraph 0041), 2006-256091 (paragraph 0027), and 2008-110522 (paragraph 0014)). According to the pre-treatment, obstacles or defects on the surface of the base material are eliminated and the surface is made smooth by modifying the surface of the base material, forming an underlayer film, or applying cleaning, thereby improving the gas barrier properties and the adhesion of the gas barrier film to be formed subsequently.